Generally, avalanches are composed of snow structures that range in volume from the volume associated with an individual snow flake to a block of consolidated snow or ice that has a volume of several cubic meters. It has been found that the snow structures with larger volumes tend to stay on or migrate towards the surface of the avalanche, while snow structures with lower volumes stay on or migrate towards the bottom of the avalanche, i.e. migrate to a location nearer to the ground and further from the surface.
One way for an individual to increase their chances of surviving an avalanche is to inflate an airbag in an airbag system that is attached to the individual to increase the volume associated with the individual. Once the airbag is inflated, the volume associated with the individual is the volume of the individual plus the volume of the inflated airbag. The greater volume associated with the individual is likely to keep the individual at the surface of the avalanche or, if buried by the avalanche, near the surface of the avalanche, thereby increasing the individual's chances of surviving the avalanche.
Generally, airbag systems for use in avalanche situations employ at least one airbag or balloon, a pressure gas cylinder for holding the pressurized gas that is used to inflate the airbag, and a valve that can be opened to release the pressurized gas to inflate the balloon in an avalanche situation. Many airbag systems also employ an element known as an ejector to reduce the amount of pressurized gas that the user of the system must carry. The ejector receives the pressurized gas from the pressure gas cylinder when the valve is opened and uses the pressurized gas to draw in ambient air to create a gas stream for inflating the airbag that is a combination of gas from the pressure gas cylinder and the drawn-in, ambient air. At least one airbag system utilizes a two-stage ejector that inflates that airbag with gas from the pressure gas cylinder and two separate streams of ambient air.